"This cat is a sister of living snow leopards -- it has a broad forehead and a short face. But it's a little smaller -- the size of clouded leopards," said lead author Dr Jack Tseng of the University of Southern California.

The new fossils were dug up in a 2010 expedition in the Zanda Basin in southwestern Tibet, by a team including Dr Tseng and his wife Juan Liu.

"We were very surprised to find a cat fossil in that basin," said Dr Tseng. "Usually we find antelopes and rhinos, but this site was special. We found multiple carnivores -- badgers, weasels and foxes."

The big cats, which include lions, tigers and leopards, diverged from their cousins Felinae, about 6.37 million years ago. The Felinae subfamily includes cougars, lynxes, and domestic cats. Palaeontologists have never been able to prove this theory before because there was a mismatch between the DNA data and fossil records. But now Panthera blytheae provides them with that missing link.

Dr. Tseng and his team will return to the basin to find more complete skeletons if possible to confirm their findings.

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